Washington: Edward Snowden, the National Security Agency (NSA) leaker, is defending his disclosure of top-secret US spying programmes in an online chat on Monday with The Guardian and is attacking US officials for calling him a traitor.

“The US government is not going to be able to cover this up by jailing or murdering me," he said. He added the government “immediately and predictably destroyed any possibility of a fair trial at home", by labelling him a traitor, and indicated he would not return to the US voluntarily.

Congressional leaders have called Snowden a traitor for revealing once-secret surveillance programmes two weeks ago in the Guardian and The Washington Post. The NSA programmes collect records of millions of Americans’ telephone calls and Internet usage as a counter-terror tool.

The disclosures revealed the scope of the collections, which surprised many Americans and have sparked debate about how much privacy the government can take away in the name of national security.

“It would be foolish to volunteer yourself to" possible arrest and criminal charges “if you can do more good outside of prison than in it", he said.

In one posted reply to a question, Snowden dismissed being called a traitor by former Vice-President Dick Cheney, who made the allegations in an interview this week on Fox News on Sunday.

Cheney was echoing a charge by Senate Intelligence Committee chair Dianne Feinstein, a Democrat. “Being called a traitor by Dick Cheney is the highest honour you can give an American, and the more panicked talk we hear from people like him, Feinstein...the better off we all are," he said.

“This is a man who gave us the warrantless wiretapping scheme as a kind of atrocity warm-up on the way to deceitfully engineering a conflict that has killed over 4,400 and maimed nearly 32,000 Americans, as well as leaving over 100,000 Iraqis dead," he added, referring to the US invasion of Iraq.

The Guardian announced that its website was hosting an online chat with Snowden, in hiding in Hong Kong, with reporter Glenn Greenwald receiving and posting his questions. The Associated Press couldn’t independently verify that Snowden was the man who posted 19 replies to questions.

In answer to a question about charges made by Cheney and other US officials that he might be spying for China, and trading information for asylum, Snowden wrote, “Ask yourself: if I were a Chinese spy, why wouldn’t I have flown directly into Beijing? I could be living in a palace petting a phoenix by now." He added later, “I have had no contact with the Chinese government."

Snowden explained that he had not flown directly to Iceland, where he has said he would like to seek asylum, because of the restrictions on travel for US government employees with top clearances that require permission 30 days in advance, making Hong Kong the more accessible option.

Snowden dismissed the US government’s claims that the NSA surveillance programmes had helped thwart dozens of terrorist attacks in more than 20 countries, including the 2009 al-Qaida plot by Afghan American Najibullah Zazi to blow up New York subways.

“Journalists should ask a specific question: ... how many terrorist attacks were prevented solely by information derived from this suspicionless surveillance that could not be gained via any other source? Then ask how many individual communications were ingested to acheive (sic) that, and ask yourself if it was worth it."

He added that “Bathtub falls and police officers kill more Americans than terrorism, yet we’ve been asked to sacrifice our most sacred rights for fear of falling victim to it."

Snowden was working as a contractor for NSA at the time he had access to the then secret programmes. He defended his actions and said he considered what to reveal and what not to, saying he did not reveal any US operations against what he called legitimate military targets, but instead showed that the NSA is hacking civilian infrastructure like universities and private businesses.

“These nakedly, aggressively criminal acts are wrong no matter the target. Not only that, when NSA makes a technical mistake during an exploitation operation, critical systems crash," he said, though he gave no examples of what systems have crashed or in which countries.

“Congress hasn’t declared war on the countries—the majority of them are our allies—but without asking for public permission, NSA is running network operations against them that affect millions of innocent people," he said.

“And for what? So we can have secret access to a computer in a country we’re not even fighting?" Snowden was referring to Prism, one of the programmes he disclosed. The programme sweeps up Internet usage data from all over the world that goes through nine major US-based Internet providers.

The NSA can look at foreign usage without any warrants, and says the programme doesn’t target Americans. US officials say the data-gathering programmes are legal and operated under secret court supervision.

Snowden explained his claim that from his desk, he could “wiretap" any phone call or email—a claim top intelligence officials have denied.

“If an NSA, FBI, CIA, DIA, etc. analyst has access to query raw SIGINT (signals intelligence) databases, they can enter and get results for anything they want," he wrote in the answer posted on the Guardian site.

The NSA did not immediately respond to an email seeking comment. But director of National Intelligence James Clapper has said that the kind of data that can be accessed and who can access it is severely limited. AP